Monday, December 30, 2013

Surveying notes for GATE, PSUs - Part 5

Hello there,
How have you been? Here is 5th part of one liners for the preparation of the GATE and PSUs.
  • Error due to curvature and refraction can be neutralized by setting the level midway between the two stations.
  • Height of instrument method of levelling is quicker and less tedious for large numbers of intermediate sights.
  • The rise and fall method provides a check on the reduction of intermediate point levels.
  • If the staff is not held vertical at a levelling station, the reduced level calculated from the observation would be less than true R.L.
  • The difference between a level line and a horizontal line is that a level line is a curved line while horizontal line is a straight line.
  • The sensitivity of a bubble tube can be increase by increasing the diameter of the bubble tube.
  • With the rise in temperature sensitivity of a bubble tube decreases, because with rise in temperature the liquid expands and bubble gets smaller.
  • Refraction correction partially eliminates the curvature correction.
  • As applied to staff readings, the corrections for curvature and refraction are respectively "-" and "+".
  • The correction for refraction as applied to staff reading is +1/7[d^2/(2R)].
  • Sensitivity of a bubble tube is designated by radius of level tube.
Thanks for visit!


Saturday, December 28, 2013

Surveying Note for GATE PSUs- part 4

Hello there,
Here is another post for your preparation of GATE and PSUs examinations.
  • A gate cap is fitted with a prismatic compass
  • The temporary adjustments of a prismatic compass are Centering, Leveling and Focusing the prism respectively in order.
  • Swinging is the process of turning the telescope about the vertical axis in horizontal plane.
  • Size of a Theodolite is specified by the diameter of the lower plate.
  • If the lower clamp screw is tightened and upper clamp screw is loosened, the Theodolite may be rotated on its inner spindle with a relative motion between the vernier and the graduated scale of lower plate.
  • A telescope is said to be inverted if its vertical circle is to its right and the bubble of the telescope is down.
  • The cross hairs in the surveying telescope  are placed much closer to the eye-piece than the objective piece.
  • For the adjustment of horizontal axis, the spire test is used for its permanent adjustment.
  • The adjustment of horizontal cross hair is required when the instrument is used for levelling.
  • Error due to displacement of the station signal can not be eliminated by repetition method of angle measurement.
  • The error due to eccentricity of inner and outer axes can be eliminated by reading both verniers and taking the mean of the two.
  • In the double application of principle of reversion, the apparent error is four times the true error.
  • Error due to line of collimation not being perpendicular to the horizontal line can be eliminated by taking mean of both face observations.
  • If a tripod settles in the interval that elapses between taking a back sight reading and the following foresight reading, then the elevation of turning point will increase.
  • If altitude bubble is provided both on index frame as well as on telescope of a theodolite, then the instrument is levelled with reference to altitude level on the index frame or altitude level on telescope if it is to be used as a level.
  • A 'level line' is a line parallel to the mean spheroidal surface of earth.
  • Turning point is the station where both back sight and fore-sights are taken
  • A rise and fall method provides us check on back-sights, foresight as well as on intermediate sights.
  • In internal focusing type of telescope a concave lens is provided.

Thanks for visit!


Thursday, December 26, 2013

Parts of a Total Station - Primary Details only

Hello There,
Are you looking for Total Station parts details? Here is it:


  • What is Total Station?
Total Station is a digital surveying instrument which has numbers of function such as, determination of elevation, horizontal distance and location of 3D-co-ordinates.

Total Station is very much precise instrument because, it uses Laser beam technology. The time taken by the LASER beam to reflect back from the target is used to calculate the distance. More time taken means more distance.

This instrument is now widely used for taking precise measurements. For the alignment of  tunnels, bridges, roads and similar other works, it is best to use a Total Station, than any other instrument which are not precise.


  • Parts of a Total Station
Here is a picture showing the primary features of a Total Station. I got this image from a Facebook friend.

Thanks for visit!

Note: Please contribute to improve this article.

Tuesday, December 24, 2013

Surveying- one liners

Hi,

Few more one liners from Surveying.

1. The tolerance for a 20 m chain is +-5mm.

2. A chain length is measured from outside end of one handle to the outside of other handle while chain is held straight.

3. Normal tension/pull is the amount of tension which neutralizes the pull and sag correction.

4. Surveying map prepared by any country are prepared with reference to the true meridian not magnetic meridian.

5. Prismatic compass has the WCB(Whole Circle bearing system) while Surveying compass has a quadrant bearing system.

6. French cross staff can be used to locate the 45 degrees and 90 degrees offset.

7. Prismatic compass has the circular graduations with zero at South and the needle attached together so, they do not move along with the box, while in surveying compass only needle is constant in North-south direction but the graduation move along with the box.

8. The horizontal angle between magnetic meridian and true meridian at a place is known as the magnetic declination of that place.

9. The difference between the fore bearing and back bearing of a line AB is 180 degrees.

10. The permissible error in the chain survey for rough and hilly areas is 1 in 250.

Thank you.

Monday, December 23, 2013

Multiple Choice Questions

Hello,

Here are the questions which I asked on my Surveying Page on Facebook, you can join me for more updates on my Facebook page.

1. A level cannot be used for
(a) Profile levelling
(b) Horizontal angle
(c) Vertical Angles
(d) Contouring

Ans : (c)

2. Alidade is used in
(a) Tachoemetry
(b) Plane Tabling
(c) Chaining
(d) Compass Surveying

Ans: (b)





       
3. Sag correction is
(a) Always positive
(b) Sometimes +ve sometimes -ve
(c) Always negative
(d) 0.

Ans: (c)

4. Principle of Chaining is

Ans: Triangulation

5. Aim/Advantage of working from whole to part is
(a) takes less time
(b) Plotting is easy
(c) Errors are reduced
(d) Need less observations
Ans: (c)

6. What is the main difference between an optical square and prism?

Ans: The angles are adjustable in optical square but they are fixed in prism.

7. A building is
(a) Obstacle for chaining but not for ranging
(b) Obstacle for ranging but not for chaining
(c) Obstacle for both chaining and ranging both.
(d) Not an obstacle to chaining or ranging.

Ans: (c)



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